Gyratory crushers comprise a vertical eccentric shaft with an inclined inner hole therein. A main shaft, into which a supporting cone is attached, and which is supported to the frame at its upper part by means of an upper supporting bearing, is mounted in the hole. The supporting cone is surrounded on its sides by the frame of the crusher, an element acting as a wearing part called outer crushing head being attached to the frame. An element acting as a wearing part called inner crushing head is attached to the supporting cone. The inner and outer crushing heads, together, form a crushing chamber, where the feed material is crushed. When the eccentric shaft is rotated, the main shaft and, together with it, the supporting cone get to an oscillating movement, whereby the gap between the inner and outer head at each point varies during the working cycle. The smallest gap during the working cycle is called the setting of the crusher, and the difference between the minimum and maximum gap is called the stroke of the crusher. Through the magnitude of the setting and the stroke of the crusher, inter alia the particle size distribution of the produced crushed material and the production capacity can be influenced.
Presently, a gyratory crusher can be adjusted by means of a hydraulic system, so that the main shaft can be moved vertically in relation to the frame. This makes it possible to change the setting so that the size of the final product corresponds to the desired one and/or to maintain the same setting when the crushing heads wear.
Dust particles and other foreign objects from the crushing chamber must be prevented from entering the bearings of the eccentric shaft and the main shaft, as well as the primary and secondary gear of the drive device, and in general the lubricant circuit inside the crusher, and through that the surfaces of the elements to be lubricated.
In the crushers of prior art, generally used presently, there is for this purpose a sealing cover around the eccentric shaft and the drive devices connected with it, attached at its lower edge to the frame, and above it as an extension a narrower cylindrical supporting sleeve for the sealing. For the upper edge of the supporting sleeve, there is an annular recess formed in the lower surface of the supporting cone. The outer surface of the supporting sleeve forms a sealing surface, against which a seal ring in the recess of the supporting cone is pressed. The seal ring glides in its recess in relation to the supporting cone along a spherical surface. In addition, when the setting of the crusher is adjusted, the seal ring glides up and down along the surface of the supporting sleeve. The ring can also glide around the supporting sleeve against the surface of the sleeve.
The most essential drawback of this prior art is that the recesses and grooves formed in the supporting cone for sealing members make the supporting cone weaker. Other drawbacks of the prior art are the complicated shape of the lower surface of the supporting cone--and thus high production costs--as well as the fast wearing of the seal ring caused by the required great movement of the seal ring.
Because in these constructions known in the art, the sealing member rises or lowers with the main shaft of the crusher when the vertical position of the main shaft is adjusted, the consequence is that also its distance from the upper supporting bearing, that is its radius of oscillation changes. For this reason, it has been necessary to dimension the sealing against the cone in this structure as a compromise between different radii of oscillation, and some clearance has been reserved to it for extreme positions.
In publication DE 673 351, there has been described a crusher, in which the sealing cover is sealed against the main shaft so, that the outer edge of a horizontal sealing member has been fitted in an internal recess provided in the upper part of the sealing cover. A drawback of this known solution is, however, that little by little the oscillating movement of the main shaft causes the sealing to break, even if it is made of flexible material. Alternatively, big clearances must be used, whereby the tightness of the construction will be lost.
In publication DE 1 243 955, there is described a crusher, in which the lower surface of the outer edge of a sealing member between the main shaft and the sealing cover is fitted tightly against the frame of the crusher. In case the main shaft is lifted upwards in order to change the setting, the sealing member departs from the surface of the crusher frame.
Publication DE 1 507 573 discloses a crusher, in which the sealing members between the main shaft and the sealing cover are completely unprotected from above, and thus subject to dust, whereby the surfaces wear very quickly. It is also not unambiguously clear from the publication, how the sealing cover and the sealing member remain in position when the setting is changed.